The present invention relates to sewing machines, and more particularly to chain-stitch sewing machines.
Before the present invention, sewing machines of the single chain-stitch type have been proposed for use in forming chain-stitches in a work piece. Such chain-stitch machines have an inherent advantage of operation over machines of the lock-stitch type, since only a single thread is required for sewing and such machines can operate at a greater efficiency.
However, certain problems have been associated with the single chain-stitch machines which have deterred construction of a completely satisfactory machine. Initially, it has been found relatively difficult in such machines to sew the work piece in any given direction in a plane, since in certain directions of work piece movement the descending needle may pass outside the previous thread loop, resulting in a missed or dropped stitch and an interruption of the stitch chain. Additionally, the sewn stitch chain may be readily unravelled from the work piece, and this result has limited the use of such chain-stitch sewing machines. In view of these shortcomings, the single thread chain-stitch machines have not been developed to permit high speed formation of chain-stitch patterns in any direction in the plane under guidance of an electrical control system with an accuracy sufficient to knot the stitch chain and prevent unravelling of the chain.